Is there a TCP Maximum Segment Size (MSS) Minimum?
I have there a OpenVPN VPN network connection, where the MSS size 60 gets send out for some reason (don't know why yet).
EDIT: Reason: OpenVPN mssfix was mistakenly set to 1
36 92.064383 10.102.0.43 10.1.151.50 TCP 52 49991 → 63760 [SYN] Seq=0 Win=65535 Len=0 MSS=60 WS=128 SACK_PERM=1
37 92.064763 10.1.151.50 10.102.0.43 TCP 52 63760 → 49991 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=256 SACK_PERM=1
There are two devices on this network, which behave different.
- Win 10 PC with Filezilla FTP Server
- Embedded device (PLC) based on VxWorks with internal FTP server
The PC sets the MSS size to 536, but the PLC sets it down to 60 like requested.
41 92.171676 10.1.151.50 10.102.0.43 FTP-DATA 576 FTP Data: 536 bytes (PASV) (RETR TCData.br)
67 17.385576 10.1.151.1 10.102.0.43 FTP-DATA 100 FTP Data: 60 bytes (PASV) (RETR TCData.br)
Is that implemented on the right way on both sides?
I know that the default TCP MSS is 536, but is there a required minimum size?
ip tcp tcpip
asked 7 hours ago
Michael UrayMichael Uray
62
add a comment |
I have there a OpenVPN VPN network connection, where the MSS size 60 gets send out for some reason (don't know why yet).
EDIT: Reason: OpenVPN mssfix was mistakenly set to 1
36 92.064383 10.102.0.43 10.1.151.50 TCP 52 49991 → 63760 [SYN] Seq=0 Win=65535 Len=0 MSS=60 WS=128 SACK_PERM=1
37 92.064763 10.1.151.50 10.102.0.43 TCP 52 63760 → 49991 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=256 SACK_PERM=1
There are two devices on this network, which behave different.
- Win 10 PC with Filezilla FTP Server
- Embedded device (PLC) based on VxWorks with internal FTP server
The PC sets the MSS size to 536, but the PLC sets it down to 60 like requested.
41 92.171676 10.1.151.50 10.102.0.43 FTP-DATA 576 FTP Data: 536 bytes (PASV) (RETR TCData.br)
67 17.385576 10.1.151.1 10.102.0.43 FTP-DATA 100 FTP Data: 60 bytes (PASV) (RETR TCData.br)
Is that implemented on the right way on both sides?
I know that the default TCP MSS is 536, but is there a required minimum size?
ip tcp tcpip
asked 7 hours ago
Michael UrayMichael Uray
62
add a comment |
I have there a OpenVPN VPN network connection, where the MSS size 60 gets send out for some reason (don't know why yet).
EDIT: Reason: OpenVPN mssfix was mistakenly set to 1
36 92.064383 10.102.0.43 10.1.151.50 TCP 52 49991 → 63760 [SYN] Seq=0 Win=65535 Len=0 MSS=60 WS=128 SACK_PERM=1
37 92.064763 10.1.151.50 10.102.0.43 TCP 52 63760 → 49991 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=256 SACK_PERM=1
There are two devices on this network, which behave different.
- Win 10 PC with Filezilla FTP Server
- Embedded device (PLC) based on VxWorks with internal FTP server
The PC sets the MSS size to 536, but the PLC sets it down to 60 like requested.
41 92.171676 10.1.151.50 10.102.0.43 FTP-DATA 576 FTP Data: 536 bytes (PASV) (RETR TCData.br)
67 17.385576 10.1.151.1 10.102.0.43 FTP-DATA 100 FTP Data: 60 bytes (PASV) (RETR TCData.br)
Is that implemented on the right way on both sides?
I know that the default TCP MSS is 536, but is there a required minimum size?
ip tcp tcpip
asked 7 hours ago
Michael UrayMichael Uray
62
I have there a OpenVPN VPN network connection, where the MSS size 60 gets send out for some reason (don't know why yet).
EDIT: Reason: OpenVPN mssfix was mistakenly set to 1
36 92.064383 10.102.0.43 10.1.151.50 TCP 52 49991 → 63760 [SYN] Seq=0 Win=65535 Len=0 MSS=60 WS=128 SACK_PERM=1
37 92.064763 10.1.151.50 10.102.0.43 TCP 52 63760 → 49991 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=256 SACK_PERM=1
There are two devices on this network, which behave different.
- Win 10 PC with Filezilla FTP Server
- Embedded device (PLC) based on VxWorks with internal FTP server
The PC sets the MSS size to 536, but the PLC sets it down to 60 like requested.
41 92.171676 10.1.151.50 10.102.0.43 FTP-DATA 576 FTP Data: 536 bytes (PASV) (RETR TCData.br)
67 17.385576 10.1.151.1 10.102.0.43 FTP-DATA 100 FTP Data: 60 bytes (PASV) (RETR TCData.br)
Is that implemented on the right way on both sides?
I know that the default TCP MSS is 536, but is there a required minimum size?
ip tcp tcpip
ip tcp tcpip
asked 7 hours ago
Michael UrayMichael Uray
62
asked 7 hours ago
Michael UrayMichael Uray
62
edited 6 hours ago
Michael Uray
asked 7 hours ago
Michael UrayMichael Uray
62
asked 7 hours ago
Michael UrayMichael Uray
62
asked 7 hours ago
Michael UrayMichael Uray
62
62
add a comment |
add a comment |
1 Answer
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536 is the minimum.
Remember that the minimum packet size for TCP (in IPv4) that all hosts must accept is 576 octets, and the MSS is the size of the payload of that packet, i.e. 576-40 = 536.
A host sending a TCP packet with MSS=60 is severely misbehaving.
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
add a comment |
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1 Answer
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active
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1 Answer
1
active
oldest
votes
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active
oldest
votes
536 is the minimum.
Remember that the minimum packet size for TCP (in IPv4) that all hosts must accept is 576 octets, and the MSS is the size of the payload of that packet, i.e. 576-40 = 536.
A host sending a TCP packet with MSS=60 is severely misbehaving.
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
add a comment |
536 is the minimum.
Remember that the minimum packet size for TCP (in IPv4) that all hosts must accept is 576 octets, and the MSS is the size of the payload of that packet, i.e. 576-40 = 536.
A host sending a TCP packet with MSS=60 is severely misbehaving.
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
add a comment |
536 is the minimum.
Remember that the minimum packet size for TCP (in IPv4) that all hosts must accept is 576 octets, and the MSS is the size of the payload of that packet, i.e. 576-40 = 536.
A host sending a TCP packet with MSS=60 is severely misbehaving.
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
536 is the minimum.
Remember that the minimum packet size for TCP (in IPv4) that all hosts must accept is 576 octets, and the MSS is the size of the payload of that packet, i.e. 576-40 = 536.
A host sending a TCP packet with MSS=60 is severely misbehaving.
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
answered 6 hours ago
Michael Hampton♦Michael Hampton
166k26305626
166k26305626
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
add a comment |
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
This is the reason why it is the default, but it does not say that it cannot be smaller.
– Michael Uray
6 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
What do you mean by that? This is extremely well documented.
– Michael Hampton♦
5 hours ago
add a comment |
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